December 2005 - WLUG - wlug.mailman3.com

getting that cpu to sleep ...
by brad 13 Dec '05

13 Dec '05

greetings, I have a question for those linux programmers out there. i'm writing a program on linux (kubuntu to be specific) that requires high-precision timing, somewhere on the order of 100 to 1000 micro seconds. I get very good timing out of a loop written such that a while() loop checks the system clock after every iteration and comparing that to the desired wait time, like so (pseudo_code): while(time_passed < wait_time) { time_passed = get_time() } ... The problem with this approach is that the process uses 99% of the CPU since it just spins the CPU until enough time has expired. My question: is there a way on linux (in C) to have the CPU sleep or send it a no-op such that it's not just eating up cycles until time expires? I have looked at nanosleep and usleep, however they appear to only have precision to 10ms which too latent for my needs. Thanks, --Brad

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Problem with gnome, Fedora core 3
by Ken Jones 10 Dec '05

10 Dec '05

Gentlemen and ladies, My Fedora Core 3 - which has been yum'd up to date - behaves strangely when using GNOME as the windows manager. The right click on blank desktop space does not work. The right click on a panel to make a new panel does not work. The result is that I can not set up any launching icons on my desktop. There is no unused space on my one (bottom) panel. The panel-disappear icon is missing. Any ideas what controls this behavior and ow I can fix it? On a different machine I have a Core4 system running GNOME perfectly. Ken Jones

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Wanted: used laptop power supply
by Andy Stewart 10 Dec '05

10 Dec '05

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 HI gang, I'm looking for a used (functioning) laptop power supply. I won't be using it for a laptop. Input: 120VAC 60Hz (standard wall socket) Output: anywhere from 12 VDC - 48 VDC at about 2 amps I need about 24 watts, so the current goes up as V goes down 48 VDC @ 0.5 A, 24 VDC @ 1.0 A, 12 VDC @ 2.0 A, etc the barrel connector will look like this neg ---C. ---pos that pic won't look right, but it is neg on outside pos on the inside Please send email if you have one, and we can negotiate a price, trade, or whatever you'd like. Ideally, you could bring it to the upcoming WLUG meeting on Wednesday, Dec 14th. Thanks! Andy - -- Andy Stewart, Founder Worcester Linux Users' Group Worcester, MA, USA http://www.wlug.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDmm/vHl0iXDssISsRAkEPAJ9FapCV+aOZmtS1wUT2VJ4/C14fCQCeI//x 9H6CbNJklxMzQbepGvSBpa0= =1Gi+ -----END PGP SIGNATURE-----

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Grub problems after imaging drive
by Dick Goodman 09 Dec '05

09 Dec '05

I recently configured a RedHat 9 system with OpenVPN . The original configuration was done on an old junk box. This is a single boot w/grub system As of last week I knew nothing about grub; I now know marginally more. As it was working successfully, it was decided to build a new box for it. The hard drive was imaged with Ghost Corporate 8.x and restored onto the new drive. There are some known issues with 8.x and grub The grub screen comes up on booting the new box, but when selecting the (one) entry for RH9, after a short pause it comes back to the grub screen. I read the grub manual, and from the grub screen did c-command, then root (hd0,0) setup (hd0) quit The messages after setup did not look like error messages. The behavior is the same, although I see a message about stage 1.5 flicker by. I figured out how to look at the hard drive with Knoppix 3.8.2 Live CD and the partitions and contents look "ok", so it appears to just be a boot issue. How do I resolve this? What additional information do you need? Is there a better way to clone Linux drive -> Linux drive? Dick

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ftp in bash script
by Gregory Avedissian 07 Dec '05

07 Dec '05

I'm writing a bash script to download a logfile from a site, archive it, then upload the archive to the site. I want the script to stop if the file doesn't download correctly, and I think I've accomplished this. (i.e. it works right when I set it up to download a non-existent file.) Question: will ftp always return an error if the file is downloaded incorrectly or incompletely? This is important, because the last part of the script will replace the file on the ftp server with a blank file of the same name. I don't want to wipe out the original logfile if I don't have it all. (secondary question: Is there a way to pass the "delete" argument without using the interactive shell?) Here's what the first section of the script looks like. Third question: If I set this up to run as a cron job, what happens to my echo messages? Will they appear in /var/log/messages? #download logfile if ftp ftp://user:password@ftp.site.net/logfile.log; then echo echo "File has been downloaded" echo else echo "Download failed" exit fi Thanks, Greg

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SSH without passwords
by Mike Leo 01 Dec '05

01 Dec '05

I remember someone talking about sharing keys between systems so you can ssh around at will without needing the password.... we are trying to do this, but are having a hard time. Anyone have a good doc (or willing to write one) about how to do this? Basically we are ssh-keygen -t (dsa/rsa) the keys, copy them to the "remote" servers ~/.ssh/ There are conflicting doc's at this point...some say you need an ssh-agent, some don't mention it. Some use passphrases, some don't. But if i have to enter an ssh passphrase everytime, why not just use the account password? Any advise would be helpful... thanks as always.. Mike

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